Glass has been etched to form a number of etched patterns on the surface of glass, which can scatter and reflect light in a random manner, resulting in reduction of the glare on the surface of the glass.
A representative example of such etching methods is a chemical etching which comprises dipping a glass in an etching composition containing strong acids such as hydrofluoric acid, nitric acid, hydrochloric acid, and sulfuric acid.
However, the strong acids used in conventional chemical etching processes cause a number of serious problems. Namely, during the etching step, poisonous gases are generated, which are harmful to humans. Also, the waste water produced should be treated in a safe manner so as not to give rise to environmental pollution, including water pollution, air pollution, and the like. Due to these problems, chemical etching has not been practiced in advanced nations on an industrial scale, and thus, can not fulfill increasing demands for non-glare glass.
In particular, hydrofluoric acid, which has been typically used in glass etching, is now recognized as causing environmental pollution, and thus is not used in many countries. Moreover, since hydrofluoric acid is very toxic, and can be fatal to humans, special care in terms of the safety and health of the handlers of the acid must be taken. For example, when skin is exposed to hydrofluoric acid, it usually induces a sharp pain and may injure or destroy the skin tissue. In addition, hydrofluoric acid vapor may cause aphasia when it enters a worker's throat upon inhalation. Also, a pulmonary edema may result if the vapor enters the lungs. In the worst case, the vapor can damage the liver and may subsequently result in death. In order to minimize the accidents that may arise from the use of hydrofluoric acid in glass etching, extensive efforts have heretofore been exerted. As a result, a variety of auxiliary facilities have been developed to prevent environmental pollution and physical injury to workers. However, these efforts do not solve all of the above mentioned problems.
Therefore, attempts have been made to reduce or avoid the use of hydrofluoric acid as it is a fundamental cause for the problems mentioned above. A representative approach involves the use of ammonium bifluoride in place of hydrofluoric acid. For example, U.S. Pat. Nos. 2,662,016 and 3,616,098 teach an etching method employing ammonium bifluoride in combination with hydrofluoric acid. U.S. Pat. No. 4,921,626 discloses a glass etching composition comprising ammonium bifluoride, xanthum gum, water, and propylene glycol.
However, the methods and compositions taught by these prior art patents are not satisfactory to etch an article of exquisite workmanship. Moreover, it is difficult for the prior art methods and compositions to obtain a fine, embossed pattern which can scatter the light when applied to the surface of glass in a random manner.
I have conducted a wide range of studies in order to solve the above mentioned problems. As a result, I have unexpectedly discovered that a number of fine, transparent, etched patterns can be formed on the surface of glass by a process which comprises applying a printing ink onto the glass; dipping the glass into a dipping solution; and washing the glass thus treated with water.